1. Field of the Invention
This invention relates generally to an optical beam deflection apparatus and in particular to a wideband optical beam deflection apparatus which utilizes a high frequency electromechanical transducer to actuate a plurality of mirrors to deflect an incoming optical beam.
2. Disclosure Statement
This disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior-art inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends upon uncertain and inevitably subjective elements of substantial likelihood and reasonableness, and inasmuch as a growing attitude appears to require citation of materials which might lead to a discovery of pertinent material, though being not of themselves pertinent.
Devices for deflecting an optical beam are useful in oscillography, in the recording and retrieval of information from an optical store and as the actuating means in an optical servo loop. Mirror galvanometers, which are commonly used in these applications, utilize a mirror mechanically coupled to a coil which moves with a magnetic field (known as a d' Arsonval mirror galvanometer). Those mirror galvanometers with the smallest mirrors may have a useful frequency response up to several thousand hertz, but the frequency response drops sharply as the mass of the mirror increases. The use of small mirrors, however, limits the aperture of the optical beam that may be used with them.
Where higher frequency response is required, acousto-optical deflectors have been used. Acousto-optical deflectors have a frequency response up to one megahertz, however, these devices are comparatively expensive. Furthermore, acousto-optical deflectors require signal processing electronics and well-collimated monochromatic radiation, as well as requiring careful angular adjustment with respect to the optical beam to be deflected.
Various optical beam deflection devices are disclosed in the prior art. For example, U.S. Pat. No. 3,902,783 discloses a beam deflector having a pair of piezoelectric transducers which have opposite states of expansion and contraction, the transducers both being connected to a rocker which rotates a pair of mirrors.
U.S. Pat. No. 3,753,199 discloses a beam deflector having a pair of piezoelectric transducers rigidly cantilevered at one end from a support member and articulately connected at the other end to a mirror.
U.S. Pat. No. 3,612,642 discloses an optical scanner having first and second mirrors mounted on the tines of an electronically driven torsional tuning fork, the mirrors being oscillated thereby. An incoming beam of light is directed toward the first mirror which reflects it onto the second mirror, the second mirror directing the beam onto a fixed third mirror. The third mirror acts to duplex the beam by directing it back ot the second mirror, which returns its beam to the first mirror.